As it is widely known, the power delivered by an internal-combustion engine depends on the amount of fuel fed to the combustion chamber, which itself depends on the amount of air fed to the combustion chamber of this engine, this amount of air being also proportional to the density of this air.
Thus, it is usual to increase this amount of air through compression of the outside air before it is allowed into the combustion chamber. This operation, known as supercharging, can be carried out using any means such as a turbocharger or a driven compressor, which can be a centrifugal or a positive-displacement compressor.
In case of supercharging using a turbocharger, the latter comprises a rotary single-flow or double-flow turbine connected by a shaft to a rotary compressor. The exhaust gases from the engine flow through the turbine, which is then rotated. This rotation is thereafter transmitted to the compressor which, by its rotation, compresses the outside air before it is fed to the combustion chamber.
As is better described in French patent application No. 2,478,736, it is intended to increase the compression of the outside air by the compressor even further so as to be able to significantly raise this amount of compressed air in the compression chamber of the engine.
This is achieved in particular by increasing the rotational speed of the turbine and therefore of the compressor.
Part of the compressed air exiting the compressor is therefore diverted in order to be directly allowed to the turbine inlet while mixing with the exhaust gases. This turbine is then traversed by a larger amount of fluid (mixture of compressed air and exhaust gas), which allows the rotational speed of the turbine, and therefore of the compressor, to be increased. This compressor speed increase thus allows to raise the pressure of the outside air that is compressed in this compressor prior to being fed to the combustion chamber of the engine.
Thus, the compressed air has a higher density, which allows the amount of air contained in the combustion chamber to be increased.
This type of supercharged engine, although satisfactory, however involves some not insignificant drawbacks.
Indeed, the flow of compressed air admitted at the turbine inlet is not correctly controlled, which may lead to dysfunctional engines.
Thus, by way of example, in case of too large amounts of compressed air diverted to the turbine inlet, the exhaust gases entering the turbine are cooled too much by this air, which causes a decrease in the overall supercharging efficiency.
The present invention aims to overcome the aforementioned drawbacks with a device for controlling the amount of air fed to the intake of a supercharged internal-combustion engine which allows to meet all engine power requirements. Furthermore, the embodiment of the present invention is intended to make modifications to the engine cylinder head so that the compressed air partial transfer ducts lead to the vicinity of the exhaust valves, which in addition favours cooling thereof. The conventional compressed air loop is not modified.
The invention disclosed here also allows to conduct a compressed air transfer from the intake to the exhaust, even when the average pressure of the compressed air at the intake is lower than that of the gases at the exhaust. All that is needed is phases during the engine running cycle where the pressure at the intake is higher than the pressure prevailing at the exhaust.